Hello,
On 11/13/10 3:09 PM, Iñaki Baz Castillo wrote:
2010/11/12 Daniel-Constantin Mierlamiconda@gmail.com:
The idea is to receive the 486 from the carrier and not send the INVITE SDP back to the carrier, this is causing the carrier to send a 482 loop detected.
First, if you create a new branch and send to same SIP gateway and you get loop detected, then the gateway is broken. It does not see that there is a different branch value in the top Via header.
Hi Daniel, the 482 reply is correct:
I expected the r-uri changes as well (serial forking). In regard to this similar case, there is a difference between loop detection and spirals, maybe sorted out in a follow-up rfc.
Cheers, Daniel
RFC 3261 - 8.2.2.2 Merged Requests
If the request has no tag in the To header field, the UAS core MUST check the request against ongoing transactions. If the From tag, Call-ID, and CSeq exactly match those associated with an ongoing transaction, but the request does not match that transaction (based on the matching rules in Section 17.2.3), the UAS core SHOULD generate a 482 (Loop Detected) response and pass it to the server transaction. The same request has arrived at the UAS more than once, following different paths, most likely due to forking. The UAS processes the first such request received and responds with a 482 (Loop Detected) to the rest of them.
This is exactly the case the user is experimenting: the INVITE arrives twice to the same server, with same From tag, Call-ID and CSeq, but different branch/transaction. So 482 is the correct response.
Regards.